1. Field of the Invention
The present invention relates to an azimuth calculation system which includes an azimuth sensor mounted on a moving body such as an automotive vehicle for calculating a direction of the moving body on a basis of the two components of the magnetic field measured in the azimuth sensor in relation to the earth's magnetism, and more particularly to a correction apparatus for the azimuth calculation system to correct various errors in the two magnetic field components caused by magnetization of the moving body.
2. Description of the Prior Art
In Japanese Patent Early Publication No. 57-148210, there has been proposed a correction method for an azimuth calculation system which comprises the steps of rotating the moving body by 360.degree. so that an azimuth circle is formed by the two magnetic field components, determining maximum and minimum values of one of the two magnetic field components on the azimuth circle to calculate a mean value of the maximum and minimum values, determining maximum and minimum values of the other magnetic field component on the azimuth circle to calculate a mean value of the maximum and minimum values, and correcting an error in the two magnetic field components on a basis of the calculated mean values. In such a conventional correction method, however, it has been found that if a portion of the azimuth circle is radially outwardly distorted due to undesired noises respectively acting on the two magnetic field components, the mean values for correction of the error will not be calculated in a precise manner due to distortion of the azimuth circle.